In general, integrated circuits (also referred to as chip or microchip) can be used to process digital or analog signals. An integrated circuit may include a plurality of circuit modules, each circuit module of which provides one or a plurality of functions of the integrated circuit. The more circuit modules the integrated circuit or chip includes, the more complex the latter and its circuit modules can be. By way of example, a complex chip can require a voltage supply, a voltage rectification, a level shifting, a DC voltage conversion, a clock generation, a power amplification, a read-out amplification or the like, which can be provided by means of a respective circuit module.
In general, a signal processing chip is striven for which has a signal-to-noise ratio which illustratively is as high as possible. Said ratio can depend on all the circuit modules of a chip since their noise is superimposed along the signal chain of the chip to form a complex interplay which ultimately limits the technically achievable signal-to-noise ratio, e.g. to approximately 60 decibels or less. By way of example, the noise of a voltage supply can be picked up by a power amplifier and amplified further, such that a signal output by the power amplifier has even greater noise than the voltage supply. In particular, that circuit module which generates the greatest noise can dominate the signal-to-noise ratio of the chip.
Conventionally, circuit modules are striven for which generate the least possible noise along the signal chain. In order to achieve a signal-to-noise ratio which is as high as possible, the signal chain is usually supplied with as low-noise voltage as possible. In a continuously signal processing sensor circuit of a chip, by way of example, MOSFET amplifier circuits or simple source follower amplifier circuits are used.
That parameter of the sensor circuit which is most critical for the signal-to-noise ratio is the so-called pink noise (also referred to as 1/f noise, also referred to in English as “flicker noise”), which increases as the frequency decreases. Conventionally, pink noise is optimized by enlarging the gate area of the amplifying transistor, although a greater demand for required chip area and a production method of increased difficulty have to be accepted for this.
As an alternative to an AC voltage, it is possible to use a DC voltage for supplying the sensor circuit. However, in order to generate the electrical DC voltage on the chip itself (also referred to as on-chip generation), conventionally a low efficiency must be accepted, which increases the waste heat of the chip and thus the necessity for actively cooling the chip. Furthermore, inaccuracies in the timing control, e.g. in the control of the switches for chopping the electrical DC voltage, and an increased power consumption as a result of the required timing control must be accepted. Therefore, in order to minimize the power consumption and the waste heat of the chip, a DC voltage which is as low as possible is usually used for supplying the amplifier circuit, e.g. a DC voltage of 2.5 volts or less.
Alternatively, the electrical DC voltage and/or its generation on the chip itself are/is dispensed with. Instead, either an AC voltage or a DC voltage generated externally (outside the chip) is used for supplying the amplifier circuit or the signal chain.